AUTOMATIC LICENSE PLATE DETECTION BASED ON COLOUR GRADIENT MAP

Xiaodong Huang

Capital Normal University, Beijing 100048, China

License plate detection plays a key role in traffic surveillance, speeding vehicles ticketing and vehicle detecting, and so on. However, most of the previous approaches to detect license plate experience difficulties in handling license plate with the uneven illuminations changes, complex background or tilted alignments. In this paper, we propose a method of license plate detection. License plate regions contain plate characters, frames and screws. First we propose to build the Colour Gradient Map (CGM) based on the colour gradient method. Then we perform the Niblack’s method on the Colour Gradient Map (CGM) to retrieve the candidate license plate regions. Finally, we use the template matching to remove most of background noises. Experimental results show that this approach is robust and can be effectively applied to license plate detection.